Image foring systems are known in which a light source is disposed behind an optically transparent display surface and an image generation device is interposed between the light source and the display surface and in which a display surface is a screen upon which is projected the light emitted from a light source with an image generating device interposed between the screen and the light source. One example of the former type is a liquid crystal television set while one example of the latter type is a projection type television set. These prior art image forming systems have the following problems.
In the case of the former type, the light source disposed behind the display surface is a point or line light source so that non-uniform illumination occurs on the screen. This non-uniform illumination cannot be completely eliminated even by increasing the number of light sources in accordance with the size of the screen. The non-uniform illumination makes poor the quality of the image formed on the liquid crystal television display surface, especially in the case of the liquid crystal color televisions, non-uniform illumination affects the quality of the color obtained by mixing three primary colors regardless of the sequence process or the additive process.
In the case of the latter type, the light source must be disposed in direct opposed relationship with the center of the screen so that the image generation device must be disposed in substantially directly opposed relationship with the center of the screen since it is disposed between the light source and the screen. As a result, a projector mainbody is located at a position in opposed or confronting relationship with the screen, thereby adversely affecting the viewing of the screen and also causing non-uniform illuminatin as in the case of the former type. Furthermore, when the latter type is used for the formation of a color image, it is impossible theoretically to cause the same picture elements of an image to be projected on the screen to converge through the image generation devices of three primary colors at one point unless a control means capable of detecting deviations and feeding back the detected deviations is provided.
In other words, it is in general impossible to obtain color convergence. Especially when conventional lenses are used in an optical system, every optical aberration occurs around the optical axis. In the case of a system in which three primary colors must be projected onto a screen by using respective optical axes, the convergence of three colors cannot be obtained because of aberrations even when the degree of precision of every part is improved.
In view of the above, the present invention has for its object to provide an image formation system which can primarily solve the non-uniformity of illumination on the display surface and the problem of the position at which an image generation device is placed.
Furthermore, the present invention has an object to provide an image forming system which can substantially solve the above-described problems in the case of the formation of color images.